ISO 15619:2013

INTERNATIONAL ISO
STANDARD 15619
First edition
2013-10-01
Reciprocating internal combustion
engines — Measurement method for
exhaust silencers — Sound power
level of exhaust noise and insertion
loss using sound pressure and power
loss ratio
Moteurs alternatifs à combustion interne — Méthode de mesure
pour silencieux d’échappement — Niveau de puissance acoustique du
bruit à l’échappement et perte par insertion à partir de la pression
acoustique et du rapport de perte de puissance
Reference number
©
ISO 2013
© ISO 2013
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ii © ISO 2013 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
1.1 Measurement uncertainty . 1
2 Normative references . 2
3 Terms and definitions . 2
4 Test environment . 6
4.1 General . 6
4.2 Criteria for background noise . 7
4.3 Criterion for acoustic adequacy of test environment . 9
5 Instrumentation .10
5.1 General .10
5.2 Calibration .10
6 Installation and operation of noise source under test for laboratory measurement.10
6.1 General .10
6.2 Source location .11
6.3 Installation requirements .11
6.4 Operation condition .13
7 Measurement .13
7.1 General .13
7.2 Laboratory measurement .14
7.3 Site measurement .17
8 Calculation .20
8.1 General .20
8.2 Calculation of sound power level of exhaust noise .20
8.3 Calculation of insertion loss .22
8.4 Calculation of power loss ratio .23
9 Information to be recorded .23
9.1 General .23
9.2 Description of the tested exhaust silencer and substitution pipe .23
9.3 Description of the engine on which the exhaust silencer is installed .23
9.4 Acoustic environment .23
9.5 Description of instrumentation .23
9.6 Acoustical data .23
10 Test report .24
Annex A (normative) Qualification procedures for the acoustic environment .25
Annex B (informative) Measurement procedure for pressure loss
..................................................................................30
Annex C (normative) Calculation of A-weighted sound power levels from frequency band levels .31
Annex D (normative) Sound power level under reference meteorological conditions .33
Bibliography .35
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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electrotechnical standardization.
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to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 70, Internal combustion engines.
iv © ISO 2013 – All rights reserved

Introduction
This International Standard specifies methods for measuring the sound power level of exhaust noise
and the insertion loss of exhaust silencers installed on reciprocating internal combustion engines and a
method for measuring the power loss ratio of reciprocating internal combustion engines.
Sound power level of exhaust noise, insertion loss, and transmission loss are parameters to characterize
the acoustic performance of exhaust silencers. Sound power levels of exhaust noise and insertion loss
are important parameters to characterize the acoustic matching performance of exhaust silencers
and reciprocating internal combustion engines. Transmission loss is the difference in sound power
level of exhaust noise between the noise before and after transmitting through the exhaust silencer,
which is the parameter to characterize the acoustic performance of the exhaust silencer itself and is
irrelevant with the reciprocating internal combustion engine. Power loss ratio and pressure loss are
parameters to characterize the aerodynamic performance of exhaust silencers. Power loss ratio is an
important parameter to characterize the aerodynamic matching performance of exhaust silencers
and reciprocating internal combustion engines, whereas resistance coefficient which is closely related
to pressure loss is to characterize the aerodynamic performance of the exhaust silencer itself and is
irrelevant with the reciprocating internal combustion engine on which the exhaust silencer is installed.
The matching parameters of the sound power level of exhaust noise, the insertion loss, and the power
loss ratio are used in this International Standard as the measurement parameters.
For sound power level of exhaust noise, the measurement results at 90° direction and 45° direction can be
different. The measurement results at 45° direction is slightly greater than the actual value, the measurement
results at 90° direction is much closer to the actual results. For insertion loss, the measurement results
at 90° direction and 45° direction may be different, but the measurement uncertainty at 90° direction is
smaller than that at 45° direction. Measurement at 90° direction is used for the laboratory measurement
(engineering method). The measurement at 90° or 45° direction is used for laboratory measurement
(survey method). The measurement at 45° direction is used for site measurement.
INTERNATIONAL STANDARD ISO 15619:2013(E)
Reciprocating internal combustion engines —
Measurement method for exhaust silencers — Sound
power level of exhaust noise and insertion loss using sound
pressure and power loss ratio
1 Scope
This International Standard specifies the measurement method and requirements for exhaust silencers
which is installed on reciprocating internal combustion engines, including laboratory measurement and
site measurement.
The following parameters are measured for laboratory measurement (engineering method):
— the sound power level (A-weighted or in frequency bands) of exhaust noise using sound pressure,
accuracy grade 2;
— the insertion loss (A-weighted or in frequency bands) of exhaust silencers;
— the power loss ratio of reciprocating internal combustion engines.
The following parameters are measured for site measurement and laboratory measurement (survey
method):
— the sound power level (A-weighted) of exhaust noise using sound pressure, accuracy grade 3;
— the insertion loss (A-weighted) of exhaust silencers.
NOTE 1 The aim of laboratory measurement in measuring the sound power level of exhaust noise is accuracy
grade 2 (engineering method) result. When the correction for background noise and/or the environment
conditions and/or the location of exhaust outlets cannot meet the requirements of the engineering method of this
International Standard, then accuracy grade 3 (survey method) result is obtained. The aim of site measurement
in measuring the sound power level of exhaust noise in this International Standard is accuracy grade 3 (survey
method) result.
The laboratory measurement (engineering method) of this International Standard can be used to make
acceptance tests and engineering measures. The site measurement and laboratory measurement (survey
method) of this International Standard can be used to make comparative tests.
This International Standard applies to all exhaust silencers installed on reciprocating internal
combustion engines falling within the field of application of ISO 3046-1 and other exhaust silencers, if
no suitable International Standard exists.
NOTE 2 Throughout the text, exhaust silencer is referred to as silencer and reciprocating internal combustion
engine as engine.
1.1 Measurement uncertainty
1.1.1 Engineering method
The standard deviation of reproducibility is equal to or less than 1,5 dB for A-weighted sound power
levels. In one-third octave bands, it is equal to or less than 5 dB from 50 Hz to 80 Hz, 3 dB from 100 Hz
to 160 Hz, 2 dB from 200 Hz to 315 Hz, 1,5 dB from 400 Hz to 5 000 Hz, and 2,5 dB from 6 300 Hz to
10 000 Hz. In octave bands, it is equal to or less than 5 dB for 63 Hz, 3 dB for 125 Hz, 2 dB for 250 Hz,
1,5 dB from 500 Hz to 4 000 Hz, and 2,5 dB for 8 000 Hz.
1.1.2 Survey method
The standard deviation of reproducibility is equal to or less than 4,0 dB for A-weighted sound power levels.
NOTE 1 The standard deviations listed in 1.1 are associated with the test conditions and procedures
defined in this International Standard and not with the noise source itself, including variations of installation
and/or operation conditions. They arise in part from variations between measurement laboratories, changes
in atmospheric conditions if outdoors, the geometry of the test room or outdoor environment, the acoustical
properties of the reflecting plane, absorption at the test room boundaries if indoors, background noise, and the
type and calibration of instrumentation. They are also due to variations in experimental techniques, including
the size and shape of the measurement surface, measurement distances, number and location of microphone
positions, sound source location, determination of environmental corrections, if any, and integration time. The
standard deviations are also affected by errors associated with measurements taken in the near field of the
source. Such errors depend upon the nature of the sound source, but generally increase for smaller measurement
distances and lower frequencies (below 250 Hz).
NOTE 2 If several laboratories use similar facilities and instrumentation, the results of sound power
determinations on a given source in those laboratories may be in better agreement than would be implied by the
standard deviations of 1.1.
NOTE 3 For a family of silencers, of similar size with similar sound power spectra and similar operating
conditions, the standard deviations of reproducibility may be smaller than the values given in 1.1.
NOTE 4 The standard deviations of reproducibility, as listed in 1.1, include the uncertainty associated with repeated
measurements on the same noise source under the same conditions (for standard deviations of reproducibility). This
uncertainty is usually much smaller than the uncertainty associated with interlaboratory variability.
NOTE 5 The procedures of this International Standard and the standard deviations given in 1.1 are applicable
to measurements on an individual silencer.
The measurement uncertainty depends on the standard deviation of reproducibility and on the degree
of confidence that is desired. As examples, for a normal distribution of sound power levels, there is 90 %
confidence that the true value of the sound power level of a source lies within the range ±1,645σ of the
R
measured value and a 95 % confidence that it lies within the range ±1,960σ of the measured value.
R
NOTE 6 For a normal distribution of sound power levels, there is 90 % confidence that the probability of
acceptance is 95 % and a 95 % confidence that the probability of acceptance is 97,5 %.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 3046-1:2002, Reciprocating internal combustion engines — Performance — Part 1: Declarations of power,
fuel and lubricating oil consumptions, and test methods — Additional requirements for engines for general use
ISO 3046-3:2006, Reciprocating internal combustion engines — Performance — Part 3: Test measurements
ISO 6926:1999, Acoustics — Requirements for the performance and calibration of reference sound sources
used for the determination of sound power levels
IEC 60942:2003, Electroacoustics — Sound calibrators
IEC 61260:1995, Electroacoustics — Octave-band and fractional-octave-band filters
IEC 61672-1:2002, Electroacoustics — Sound level meters — Part 1: Specifications
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2 © ISO 2013 – All rights reserved

3.1
sound pressure
p
difference between instantaneous pressure and static pressure, expressed in pascals
3.2
sound pressure level
L
p
ten times the logarithm to the base 10 of the ratio of the square of the sound pressure, p, to the square
of a reference value, p
p
L =10lg
p
p
where the reference value, p , is 20 μPa
Note 1 to entry: If specific frequency and time weightings, as specified in IEC 61672–1, and/or specific frequency
bands are applied, this is indicated by appropriate subscripts, e.g. L denotes the A-weighted sound pressure level.
pA
Note 2 to entry: It is expressed in decibels.
3.3
time-averaged sound pressure level
L
p,T
ten times the logarithm to the base 10 of the ratio of the time average of the square of the sound
pressure, p, during a stated time interval of duration, T (starting at t and ending at t ), to the square of
1 2
a reference value, p
t
 1 
pt dt
()
 
∫
T t
L =10lg 
pT,
 p 
 
 
where the reference value, p , is 20 μPa
Note 1 to entry: In general, the subscript “T” is omitted since time-averaged sound pressure levels are necessarily
determined over a certain measurement time interval.
Note 2 to entry: Time-averaged sound pressure levels are often A-weighted, in which case they are denoted by
L , , which is usually abbreviated as L .
pA T pA
Note 3 to entry: It is expressed in decibels.
3.4
surface time-averaged sound pressure level
L
P
mean (energy average) of the time-averaged sound pressure levels over all the microphone positions, or
traverses, on the measurement surface, with the background noise correction, K , and the environmental
correction, K , applied
Note 1 to entry: It is expressed in decibels.
3.5
measurement time interval
T
portion or a multiple of an operational period or operational cycle of the noise source under test for
which the time-averaged sound pressure level is determined
Note 1 to entry: It is expressed in seconds.
3.6
acoustic free field
sound field in a homogeneous, isotropic medium free of boundaries
Note 1 to entry: In practice, an acoustic free field is a field in which the influence of reflections at the boundaries
or other disturbing objects are negligible over the frequency range of interest.
3.7
reflecting plane
sound-reflecting planar surface on which the noise source under test is located
3.8
acoustic free field over a reflecting plane
acoustic free field in the half-space above an infinite reflecting plane in the absence of any other obstacles
3.9
frequency range of interest
for general purposes, the frequency range of octave bands with nominal mid-band frequencies from
63 Hz to 8 000 Hz (including one-third octave bands with mid-band frequencies from 50 Hz to 10 000 Hz)
Note 1 to entry: For special purposes, the frequency range can be extended or reduced, provided that the test
environment and instrument specifications are satisfactory for use over the modified frequency range. Changes
to the frequency range of interest are included in the test report.
3.10
measurement radius
r
radius of a spherical measurement surface
Note 1 to entry: It is expressed in metres.
3.11
measurement surface
hypothetical spherical surface of area, S, on which the microphone positions are located at which the
sound pressure levels are measured, enveloping the noise source under test
3.12
background noise
noise from all sources other than the noise source under test
Note 1 to entry: Background noise includes contributions from airborne sound, noise from structure-borne
vibration, and electrical noise in the instrumentation.
3.13
background noise correction
K
correction applied to the mean (energy average) of the time-averaged sound pressure levels over all the
microphone positions on the measurement surface, to account for the influence of background noise
Note 1 to entry: The background noise correction is frequency dependent; the correction in the case of a frequency
band is denoted by K , where f denotes the relevant mid-band frequency, and that in the case of A-weighting is
1f
denoted by K .
1A
Note 2 to entry: It is expressed in decibels.
4 © ISO 2013 – All rights reserved

3.14
environmental correction
K
correction applied to the mean (energy average) of the time-averaged sound pressure levels over all the
microphone positions on the measurement surface, to account for the influence of reflected sound
Note 1 to entry: The environmental correction is frequency dependent; the correction in the case of a frequency
band is denoted by K , where f denotes the relevant mid-band frequency, and that in the case of A-weighting is
2f
denoted by K .
2A
Note 2 to entry: In general, the environmental correction depends on the area of the measurement surface and,
usually, K increases with S.
Note 3 to entry: It is expressed in decibels.
3.15
sound power
P
through a surface, the product of the sound pressure, p, and the component of the particle velocity, u , at
n
a point on the surface in the direction normal to the surface, integrated over that surface
Note 1 to entry: The quantity relates to the rate per time at which airborne sound energy is radiated by a source.
Note 2 to entry: It is expressed in watts.
3.16
sound power level
L
W
ten times the logarithm to the base 10 of the ratio of the sound power of a source, W, to a reference value, W
W
L =10lg
W
W
where the reference value, W , is 1 pW
Note 1 to entry: If a specific frequency weighting, as specified in IEC 61672–1, and/or specific frequency bands are
applied, this is indicated by appropriate subscripts, e.g. L denotes the A-weighted sound power level.
WA
Note 2 to entry: It is expressed in decibels.
3.17
exhaust silencer
chamber with acoustic lining and/or special structure designed to reduce exhaust noise
Note 1 to entry: The ICE exhaust silencer generally comprises the entire part from its inlet but does not include
the exhaust manifold and pipe.
3.18
substitution pipe
rigid, non-absorbing pipe having the same length and the same cross section area of outlet as the
tested silencer
3.19
straight transition pipe
straight pipe used to connect two pipes of different cross section areas
3.20
bent transition pipe
bent pipe used to change the airflow direction and to connect two pipes of the same cross section area
3.21
centre distance of several exhaust outlets
b
double average distance from one exhaust outlet to the geometric centre of all exhaust outlets
3.22
insertion loss
D
I
loss of sound power due to the insertion of a component or device at some point in a transmission system
Note 1 to entry: Specifically, it is the difference between the sound power level of exhaust noise when the substitution
pipe is installed on the engine and when the exhaust silencer is installed on the engine. It is expressed in decibels.
DL=−L
I(WWSP)(ES)
where
L is the sound power level of exhaust noise when the substitution pipe is installed on the
W(SP)
engine, in decibels;
L is the sound power level of exhaust noise when the silencer is installed on the engine, in
W(ES)
decibels.
3.23
power loss ratio
r
p
ratio of the difference between the engine power when the substitution pipe is installed on the engine
and when the exhaust silencer is installed on the engine, to the engine power with the substitution pipe
installed on the engine in the declared condition
Note 1 to entry: It is expressed in percentage.
PP−
r(SP) r(ES)
r = ×100%
P
P
r(SP)
where
is the engine power when the substitution pipe is installed on the engine under stand-
P
r(SP)
ard reference condition, in kilowatts;
P is the engine power when the exhaust silencer is installed on the engine under standard
r(ES)
reference condition, in kilowatts.
4 Test environment
4.1 General
Environmental conditions having an adverse effect on the microphones used for the measurements
(e.g. strong electric or magnetic fields, wind, impingement of air discharge from the noise source being
tested, high temperatures) shall be avoided. The instructions of the manufacturer of the measuring
instrumentation regarding adverse environmental conditions shall be followed.
In an outdoor area, care shall be taken to minimize the effects of adverse meteorological conditions
(e.g. temperature, humidity, wind, precipitation) on sound propagation and sound generation over the
frequency range of interest or on the background noise during the course of the measurements.
6 © ISO 2013 – All rights reserved

When a reflecting surface is not a ground plane or is not an integral part of a test room surface,
particular care should be exercised to ensure that the plane does not radiate any appreciable sound due
to vibrations.
4.1.1 Engineering method
The test environments that are applicable for measurements in accordance with this International
Standard are the following:
a) a laboratory room or a flat outdoor area which is adequately isolated from background noise (see
4.2) and which provides an acoustic free field over a reflecting plane;
b) a room or a flat outdoor area which is adequately isolated from background noise (see 4.2) and
in which an environmental correction can be applied to allow for a limited contribution from the
reverberant field to the sound pressures on the measurement surface.
4.1.2 Survey method
The test environment that is applicable for measurements in accordance with this International Standard
is a room or a flat outdoor area which is adequately isolated from background noise (see 4.2) and which
meets the qualification requirements of 4.3.
4.2 Criteria for background noise
4.2.1 Engineering method relative criteria
4.2.1.1 General
The time-averaged sound pressure level of the background noise measured and averaged (see 8.2.1) over
the microphone positions or traverses on the measurement surface shall be at least 6 dB, and preferably
more than 15 dB, below the corresponding uncorrected time-averaged sound pressure level of the noise
source under test when measured in the presence of this background noise. For measurements in frequency
bands, this requirement shall be met in each frequency band within the frequency range of interest.
If this requirement is met, the background noise criteria of this International Standard are satisfied.
4.2.1.2 Frequency band measurements
The requirements of 4.2.1.1 may not be achievable in all frequency bands, even when the background
noise levels in the test room are extremely low and well controlled. Therefore, any band within the
frequency range of interest in which the A-weighted sound power level of the noise source under test is
at least 15 dB below the highest A-weighted band sound power level may be excluded from the frequency
range of interest for the purposes of determining compliance with the criteria for background noise.
4.2.1.3 A-weighted measurements
If the A-weighted sound power level is to be determined from frequency band levels and reported,
the following steps shall be followed to determine whether this quantity meets the background noise
criteria of this International Standard.
a) The A-weighted sound power level is computed in accordance with the procedures in this International
Standard using the data from every frequency band within the frequency range of interest.
b) The computation is repeated, but excluding those bands for which ΔL < 6 dB.
p
If the difference between these two levels is less than 0,5 dB, the A-weighted sound power level
determined from the data for all bands may be considered as conforming to the background noise
criteria of this International Standard.
4.2.2 Absolute criteria
If it can be demonstrated that the background noise levels in the test room at the time of the measurements
are less than or equal to those given in Table 1 for all bands within the frequency range of interest, the
measurements can be taken as having met the background noise requirements of this International
Standard, even if the 6 dB requirement (see 4.2.1.1) is not met for all bands. It can be assumed that the
source emits little or no measurable noise in these frequency bands and that the data reported represent
an upper bound to the sound power level in these bands.
In the case where some of the measured time-averaged levels from the source under test are less than
or equal to those given in Table 1, the frequency range of interest may be restricted to a contiguous
range of frequencies that includes both the lowest and highest frequencies at which the sound pressure
level from the noise source exceeds the corresponding value in Table 1. In such cases, the applicable
frequency range of interest shall be reported.
4.2.3 Statement of non-conformity with criteria
If neither the relative criteria of 4.2.1 nor the absolute criteria in 4.2.2 are met, the report shall clearly
state that the background noise requirements of this International Standard have not been met and,
in the case of frequency band measurements, shall identify the particular frequency bands that do not
meet the criteria. Furthermore, the report shall not state or imply that the measurements have been
made “in full conformity” with this International Standard.
Table 1 — Maximum background noise levels in the test room for absolute criteria
Maximum band sound pressure
One-third octave mid-band frequency
level
Hz
dB
50 44
63 38
80 32
100 27
125 22
160 16
200 13
250 11
315 9
400 8
500 7
630 7
800 7
1 000 7
1 250 7
1 600 7
2 000 7
2 500 8
3 150 8
4 000 8
5 000 8
6 300 8
8 © ISO 2013 – All rights reserved

Table 1 (continued)
Maximum band sound pressure
One-third octave mid-band frequency
level
Hz
dB
8 000 12
10 000 14
4.2.4 Survey method
The A-weighted sound pressure levels due to background noise averaged over the microphone positions
shall be at least 3 dB below the mean sound pressure level due to the noise source under test in operation
when measured in the presence of this background noise (see 8.2.1).
4.3 Criterion for acoustic adequacy of test environment
4.3.1 Engineering method
4.3.1.1 General
A test room shall provide a measurement surface that lies inside a sound field that is essentially free of
undesired sound reflections from the room boundaries or nearby objects (apart from the floor).
As long as it is practicable, the test environment shall be free from reflecting objects other than the
reflecting plane(s).
NOTE 1 An object in the proximity of the noise source under test can be considered to be sound reflecting if its
width (e.g. diameter of a pole or supporting member) exceeds one-tenth of its distance from the reference box.
The reflecting plane(s) shall extend at least 0,5 m beyond the projection of the measurement surface on
the plane(s). The sound absorption coefficient of the reflecting plane(s) shall be less than 0,1 over the
frequency range of interest.
NOTE 2 Smooth concrete or smooth sealed asphalt surface(s) are generally satisfactory.
Annex A specifies procedures for determining the magnitude of the environmental correction, K , to
account for deviations of the test environment from the ideal condition. Measurements in accordance
with this International Standard are only valid where K ≤ 4 dB.
2A
The environmental correction, K , is assumed to be zero for measurements made in hemi-anechoic
rooms which meet the requirements of ISO 3745.
For an outdoor space which consists of a hard, flat ground surface, such as asphalt or concrete, with no
sound-reflecting objects within a distance from the noise source equal to 10 times the greatest distance
from the geometric centre of the source to the lowest measurement points, it shall be assumed that the
environmental correction K is less than 0,5 dB and can be neglected.
4.3.1.2 Criterion for environmental correction
The environmental correction, K , shall first be determined without reference to frequency band data,
2A
using one of the procedures of Annex A. Then
a) if K > 4 dB, this International Standard is not applicable, and
2A
b) if K ≤ 4 dB, measurements may be made in accordance with this International Standard, either in
2A
frequency bands or A-weighted.
Where it is decided to make measurements in frequency bands, the relevant environmental correction
K2 shall be determined in each band over the frequency range of interest in accordance with A.2 or A.3.4
and all measurements to determine LW of a noise source shall be made in frequency bands. LWA shall be
calculated using the frequency-band levels (see Annex C).
4.3.2 Survey method
Annex A specifies procedures for determining the magnitude of the environmental correction, K , to
2A
account for deviations of the test environment from the ideal condition. Measurements in accordance
with this International Standard are only valid where K ≤ 7 dB.
2A
5 Instrumentation
5.1 General
The instrumentation system, including the microphones, cables, and windscreens, if used, shall meet
the requirements of IEC 61672-1:2002, class 1 for results of accuracy grade 2 and class 2 for results of
accuracy grade 3, and the filters shall meet the requirements of IEC 61260:1995, class 1.
5.2 Calibration
Before and after each series of measurements, a sound calibrator meeting the requirements of
IEC 60942:2003, class 1 shall be applied to each microphone to verify the calibration of the entire
measuring system at one or more frequencies within the frequency range of interest. Without any
adjustment, the difference between the readings made before and after each series of measurements
shall be less than or equal to 0,5 dB. If this value is exceeded, the results of the series of measurements
shall be discarded.
The calibration of the sound calibrator, the compliance of the instrumentation system with the
requirements of IEC 61672-1, the compliance of the filter set with the requirements of IEC 61260, and, if
used, the compliance of the reference sound source with the requirements of ISO 6926 shall be verified
at intervals in a laboratory making calibrations traceable to appropriate standards.
Unless national regulations dictate otherwise, it is recommended that the sound calibrator should be
calibrated at intervals not exceeding 1 y, the reference sound source should be calibrated at intervals not
exceeding 2 y, the compliance of the instrumentation system with the requirements of IEC 61672-1 should
be verified at intervals not exceeding 2 y, and the compliance of the filter set with the requirements of
IEC 61260 should be verified at intervals not exceeding 2 y.
6 Installation and operation of noise source under test for laboratory measurement
6.1 General
The manner in which the silencer under test is installed and operated may have a significant influence
on the sound power emitted by a noise source, for example, the shape, inner diameter, and length of the
exhaust outlet may have influence on the sound power and/or power loss ratio. The flow noise generated
by high-flow speed can be greater due to the smaller inner diameter of the exhaust outlet. The silencer
to be tested shall be installed with respect to, as if it were in normal use. This clause specifies conditions
that are intended to minimize variations of the sound power level due to the installation and operating
conditions of the noise source under test.
10 © ISO 2013 – All rights reserved

6.2 Source location
6.2.1 Engineering method
The exhaust outlet shall be installed outdoors or in a test room which meets the requirements of accuracy
grade 2 (engineering method) and is not the same room where the engine is. For the requirements of
exhaust outlet location, see Table 2; for the requirements of measurement radius r, see 7.2.1.1.
NOTE If the location of the exhaust outlet cannot meet the requirements of the engineering method, see 6.2.2.
6.2.2 Survey method
The exhaust outlet and the engine are installed in the same room, and the measurement result of the
sound power level of accuracy grade 3 (survey method) is obtained. For the requirements of exhaust
outlet location, see Table 2; for the requirements of measurement radius r, see 7.2.1.2
Table 2 — Requirements of exhaust outlet location
Dimensions in metres
Parameters Engineering method Survey method
distance between exhaust outlet and
d ≥ r and d ≥ 0,5 d ≥ r and d ≥ 0,25
1 1 1 1
reflecting planes (ground), d
distance between exhaust outlet and
d ≥ 2r d ≥ 2r
2 2
wall/ceiling at flow direction, d
distance between exhaust outlet and
d ≥ r and d ≥ 0,5 d ≥ r and d ≥ 0,25
3 3 3 3
wall/ceiling at non-flow direction, d
6.3 Installation requirements
6.3.1 General
If the exhaust outlet installed outdoors or in a test room which is not the same room where the engine is,
sound insulation and vibration isolation shall be made between the exhaust pipe and walls.
If the exhaust outlet and the engine are installed in the same room, the excessive noise generated by the
engine and the dynamometer as one part of background noise shall be shielded or wrapped to meet the
requirements of criteria for background noise (see 4.2) to reduce extraneous noise influencing the noise
radiated from the exhaust outlet.
6.3.2 Straight transition pipe
If the inner diameter of the exhaust pipe and/or substitution pipe and the inner diameter of the inlet
of the silencer are different, use a straight transition pipe to connect them (see Figure 1). The use of a
straight transition pipe shall meet the requirement of Formula (1).
l
≥28, (1)
aa−
in out
where
is the inner diameter of the inlet of the exhaust silencer, in metres;
a
in
a is the inner diameter of the outlet of the exhaust silencer or equivalent inner diameter for
out
several exhaust outlets (area calculated using the equivalent inner diameter are the sum
of all cross-section areas of exhaust outlets), in metres;
l is the length of the straight transition pipe, in metres.
Figure 1 — Straight transition pipe (schematic)
6.3.3 Bent transition pipe
The bent transition pipe shall be used to change the direction of airflow (see Figure 2). If used, it shall
meet the requirement of Formula (2).
R
≥2 (2)
dp
where
R is the radius, in metres;
d is the diameter of the steel pipe, in metres.
p
12 © ISO 2013 – All rights reserved

Figure 2 — Bent transition pipe (schematic)
NOTE Minimize the number of bent transition pipes which influence the measurement results of tested
parameters.
6.4 Operation condition
For the laboratory measurement, the engine shall be operated at its ISO standard power and speed as
defined in ISO 3046-1 under ISO standard reference conditions in a steady state when the substitution
pipe is installed on the engine. The engine shall be operated under ISO standard reference conditions
when the exhaust silencer is installed on the engine, keeping the throttle opening unchanged as the
condition of the substitution pipe installed on the engine is in a steady state. The temperature of the
oil, coolant, and tested silencer shall be stable when the engine is operated in a steady state, where the
ambient and intake temperature shall not be higher than 45°C.
Measurements can be made in other operating conditions and, if necessary, can also be made in accelerated
or decelerated conditions. All measurements made in such conditions shall be stated in the test report.
7 Measurement
7.1 General
This International Standard specifies two measurement methods: laboratory measurement and site
measurement. Laboratory measuremen
...